A phase I open-label, dose-escalation study of NUC-3373, a targeted thymidylate synthase inhibitor, in patients with advanced cancer (NuTide:301).

PURPOSE: 5-fluorouracil (5-FU) is inefficiently converted to the active anti-cancer metabolite, fluorodeoxyuridine-monophosphate (FUDR-MP), is associated with dose-limiting toxicities and challenging administration schedules. NUC-3373 is a phosphoramidate nucleotide analog of fluorodeoxyuridine (FUDR) designed to overcome these limitations and replace fluoropyrimidines such as 5-FU. PATIENTS AND METHODS: NUC-3373 was administered as monotherapy to patients with advanced solid tumors refractory to standard therapy via intravenous infusion either on Days 1, 8, 15 and 22 (Part 1) or on Days 1 and 15 (Part 2) of 28-day cycles until disease progression or unacceptable toxicity. Primary objectives were maximum tolerated dose (MTD) and recommended Phase II dose (RP2D) and schedule of NUC-3373. Secondary objectives included pharmacokinetics (PK), and anti-tumor activity. RESULTS: Fifty-nine patients received weekly NUC-3373 in 9 cohorts in Part 1 (n = 43) and 3 alternate-weekly dosing cohorts in Part 2 (n = 16). They had received a median of 3 prior lines of treatment (range: 0-11) and 74% were exposed to prior fluoropyrimidines. Four experienced dose-limiting toxicities: two Grade (G) 3 transaminitis; one G2 headache; and one G3 transient hypotension. Commonest treatment-related G3 adverse event of raised transaminases occurred in < 10% of patients. NUC-3373 showed a favorable PK profile, with dose-proportionality and a prolonged half-life compared to 5-FU. A best overall response of stable disease was observed, with prolonged progression-free survival. CONCLUSION: NUC-3373 was well-tolerated in a heavily pre-treated solid tumor patient population, including those who had relapsed on prior 5-FU. The MTD and RP2D was defined as 2500 mg/m2 NUC-3373 weekly. NUC-3373 is currently in combination treatment studies. TRIAL REGISTRATION: Clinicaltrials.gov registry number NCT02723240. Trial registered on 8th December 2015. https://clinicaltrials.gov/study/NCT02723240 .

High OXPHOS efficiency in RA-FUdr-differentiated SH-SY5Y cells: involvement of cAMP signalling and respiratory supercomplexes.

Neurons are highly dependent on mitochondria to meet their bioenergetic needs and understanding the metabolic changes during the differentiation process is crucial in the neurodegeneration context. Several in vitro approaches have been developed to study neuronal differentiation and bioenergetic changes. The human SH-SY5Y cell line is a widely used cellular model and several differentiation protocols have been developed to induce a neuron-like phenotype including retinoic acid (RA) treatment. In this work we obtained a homogeneous functional population of neuron-like cells by a two-step differentiation protocol in which SH-SY5Y cells were treated with RA plus the mitotic inhibitor 2-deoxy-5-fluorouridine (FUdr). RA-FUdr treatment induced a neuronal phenotype characterized by increased expression of neuronal markers and electrical properties specific to excitable cells. In addition, the RA-FUdr differentiated cells showed an enrichment of long chain and unsaturated fatty acids (FA) in the acyl chain composition of cardiolipin (CL) and the bioenergetic analysis evidences a high coupled and maximal respiration associated with high mitochondrial ATP levels. Our results suggest that the observed high oxidative phosphorylation (OXPHOS) capacity may be related to the activation of the cyclic adenosine monophosphate (cAMP) pathway and the assembly of respiratory supercomplexes (SCs), highlighting the change in mitochondrial phenotype during neuronal differentiation.

Feeding on lactic acid bacteria isolated from food extends the lifespan of Caenorhabditis elegans.

Lactic acid bacteria (LAB) contribute to human health, and LAB functionality has been studied using Caenorhabditis elegans as an alternative host. However, many studies have focused on the efficacy of a single strain of LAB, and few reports have compared various LAB strains. In this study, we examined the effects of 15 strains of LAB isolated from vegetables, meat, and fermented foods on nematode longevity and healthy lifespan. To reduce the frequency of laborious survival observations, we performed a lifespan assay on agar plates containing 2'-deoxy-5-fluorouridine (FUdR), which inhibits egg hatching and prevents generation mixing. Four beneficial strains showed significant lifespan extension and increased spontaneous nematode mobility, regardless of treatment with or without FUdR and the frequency of survival observation. These results suggested increased longevity and an extended healthy lifespan, confirming the reliability of our method. The four strains are expected to show anti-ageing effects besides longevity and have effects on age-related degenerative diseases. Our labor-saving method can be used as an alternative to conventional methods and enable simultaneous screening of multiple strains. Future research could explore factors contributing to lifespan regulation by comparing and verifying differential strain effects on lifespan.

Deciphering the binding mode and structural perturbations in floxuridine-human serum albumin complexation with spectroscopic, microscopic, and computational techniques.

The binding mode of antineoplastic antimetabolite, floxuridine (FUDR), with human serum albumin (HSA), the leading carrier in blood circulation, was ascertained using multi-spectroscopic, microscopic, and computational techniques. A static fluorescence quenching was established due to decreased Ksv values with rising temperatures, suggesting FUDR-HSA complexation. UV-vis absorption spectral results also supported this conclusion. The binding constant, Ka values, were found within 9.7-7.9 × 103 M-1 at 290, 300, and 310 K, demonstrating a moderate binding affinity for the FUDR-HSA system. Thermodynamic data (ΔS = +46.35 J.mol-1.K-1 and ΔH = -8.77 kJ.mol-1) predicted the nature of stabilizing forces (hydrogen-bonds, hydrophobic, and van der Waals interactions) for the FUDR-HSA complex. Circular dichroism spectra displayed a minor disruption in the protein's 2° and 3° structures. At the same time, atomic force microscopy images proved variations in the FUDR-HSA surface morphology, confirming its complex formation. The protein's microenvironment around Trp/Tyr residues was also modified, as judged by 3-D fluorescence spectra. FUDR-bound HSA showed better resistance against thermal stress. As disclosed from ligand displacement studies, the FUDR binding site was placed in subdomain IIA (Site I). Further, the molecular docking analysis corroborated the competing displacement studies. Molecular dynamics evaluations revealed that the complex achieved equilibrium during simulations, confirming the FUDR-HSA complex's stability.

Case-Based Clinical Guidance on Dosing and Management of the Hepatic Artery Infusion Chemotherapy Pump.

Hepatic artery infusion (HAI) delivers localized high-dose floxuridine directly to liver tumors through an implanted pump. While patients are undergoing active treatment, the pump is refilled with chemotherapy alternating with saline every 2 weeks using a specialized noncoring needle. Numerous clinical scenarios influence the dosing of floxuridine, which do not conform to the usual dose modification schema for systemic chemotherapy. This article aims to provide practical clinical management solutions to overcome the common challenges faced by oncologists in the real-world management of HAI pump therapy.

Enhancing or Quenching of a Mitochondria-Targeted AIEgens-Floxuridine Sensor by the Regulation of pH-Dependent Self-assembly, Efficient Recognition of Hg2+, and Stimulated Response of GSH.

Biocompatible fluorescent probes have emerged as essential tools in life sciences for visualizing subcellular structures and detecting specific analytes. Herein, we report the synthesis and characterization of a novel fluorescent probe (TPE-FdU), incorporated with hydrophilic 2'-fluoro-substituted deoxyuridine and hydrophobic ethynyl tetraphenylethene moieties, which possessed typical aggregation-induced emission (AIE) behavior. In comparison to the TPE-FdU (pKa 7.68) treated in neutral conditions, it performed well at pH 4, exhibiting an enhanced 450 nm emission signal of approximately four times stronger. As the pH value was increased to 10, the fluorescence intensity was completely quenched. The TEM images of TPE-FdU in an acidic environment (nanospherical morphology, AIE enhance, pH = 4) and in a basic environment (microrods, fluorescence quenching, pH = 9) revealed that it was a pH-dependent self-assembled probe, which was also illustrated by the interpretation of the NMR spectrum. Furthermore, the TPE-FdU probe exhibited a specific response to trace Hg2+ ions. Interestingly, the quenched fluorescence of the TPE-FdU probe caused by Hg2+ can be recovered by the addition of GSH due to the formation of the Hg-S bond being released away. MTT assay and CLSM images demonstrated that TPE-FdU was nontoxic and selectively visualized in the intracellular mitochondria. These results contributed to the development of advanced fluorescent probes with diverse applications in cell imaging, environment protection, and biomedical research.

Effects of six pyrimidine analogs on the growth of Tetrahymena thermophila and their implications in pyrimidine metabolism.

Tetrahymena are ciliated protists that have been used to study the effects of toxic chemicals, including anticancer drugs. In this study, we tested the inhibitory effects of six pyrimidine analogs (5-fluorouracil, floxuridine, 5'-deoxy-5-fluorouridine, 5-fluorouridine, gemcitabine, and cytarabine) on wild-type CU428 and conditional mutant NP1 Tetrahymena thermophila at room temperature and the restrictive temperature (37°C) where NP1 does not form the oral apparatus. We found that phagocytosis was not required for pyrimidine analog entry and that all tested pyrimidine analogs inhibited growth except for cytarabine. IC50 values did not significantly differ between CU428 and NP1 for the same analog at either room temperature or 37°C. To investigate the mechanism of inhibition, we used two pyrimidine bases (uracil and thymine) and three nucleosides (uridine, thymidine, and 5-methyluridine) to determine whether the inhibitory effects from the pyrimidine analogs were reversible. We found that the inhibitory effects from 5-fluorouracil could be reversed by uracil and thymine, from floxuridine could be reversed by thymidine, and from 5'-deoxy-5-fluorouridine could be reversed by uracil. None of the tested nucleobases or nucleosides could reverse the inhibitory effects of gemcitabine or 5-fluorouridine. Our results suggest that the five pyrimidine analogs act on different sites to inhibit T. thermophila growth and that nucleobases and nucleosides are metabolized differently in Tetrahymena.

Starting a successful hepatic artery infusion pump program: A practical guide.

Implementation of a successful hepatic artery infusion pump program requires numerous factors to be in place, and the lack of any of these may lead to program failure. First and foremost, hepatic artery infusion pump programs must have adequate surgical expertise in the complex technical aspects of hepatic artery infusion pump implantation and postoperative management. Most new hepatic artery infusion pump programs are initiated by a surgeon and led in conjunction with a medical oncologist. Medical oncology experience in floxuridine dosing is critical in maximizing the treatment doses and the number of cycles administered while avoiding biliary toxicity. This is facilitated by collaboration with an engaged pharmacy team. To have adequate patient volume for a successful program, internal and external stakeholders must have buy-in, including surgical and medical oncology colleagues unfamiliar with hepatic artery infusion pumps, colorectal surgery, and other referring providers. Programmatic support must be obtained from the hospital, cancer center, and department administration. Day-to-day pump access for chemotherapy and maintenance saline fills must be performed by appropriately trained infusion nurses to avoid complications. Nuclear and diagnostic radiology experience is key to identifying extrahepatic perfusion and hepatic artery infusion pump-specific complications. Additionally, skilled interventional radiologists and gastroenterologists are necessary to identify and treat rare complications rapidly. Finally, given the current rapid expansion of hepatic artery infusion pump programs, new programs must identify engaged mentors to help guide patient selection, navigate the nuanced issues that may arise, and provide advice in the case of complications. Although hepatic artery infusion pump dissemination outside of several major tertiary centers previously had stalled, establishing a successful and active hepatic artery infusion pump is feasible with appropriate training, mentorship, and thoughtful assembly of a dedicated multidisciplinary team.

Systemic exposure of floxuridine after hepatic arterial infusion pump chemotherapy with floxuridine in patients with resected colorectal liver metastases.

BACKGROUND: Floxuridine's high hepatic extraction ratio and short elimination half-life allows maximum liver exposure with minimal systemic side-effects. This study attempts to quantify the systemic exposure of floxuridine. METHODS: Patients undergoing continuous hepatic arterial infusion pump (HAIP) floxuridine after resection of colorectal liver metastases (CRLM) in two centres underwent six cycles of floxuridine at start dose 0.12 mg/kg/day. No concomitant systemic chemotherapy was administered. Peripheral venous blood samples were drawn during the first two cycles: pre-dose (only in the second cycle), 30 min, 1 h, 2 h, 7 h, and 15 days after floxuridine infusion. Foxuridine concentration in the residual pump reservoir was measured on day 15 of both cycles. A floxuridine assay with a lower boundary of detection of 0.250 ng/mL was developed. RESULTS: 265 blood samples were collected in the 25 patient included in this study. Floxuridine was mostly measurable at day 7 and day 15 (86 % and 88 % of patients respectively). The median dose corrected concentrations were 0.607 ng/mL [IQR: 0.472-0.747] for cycle 1 day 7, 0.579 ng/mL [IQR: 0.470-0.693] for cycle 1 day 15, 0.646 ng/mL [IQR: 0.463-0.8546] for cycle 2 day 7, and 0.534 ng/mL [IQR: 0.4257-0.7075] for cycle 2 day 15. One patient had remarkably high floxuridine concentrations reaching up to 44 ng/mL during the second cycle, without a clear explanation. The floxuridine concentration in the pump decreased by 14.7 % (range 0.5 %-37.8 %) over a period of 15 days (n = 18). CONCLUSION: Overall, negligible systemic concentrations of floxuridine were detected. However, remarkably increased levels were detected in one patient. Floxuridine concentration in the pump decreases over time.

Evaluation of biliary toxicity in patients with hepatic artery infusion pumps.

PURPOSE: Identify risk factors for biliary toxicity in patients with colorectal liver metastases who received floxuridine (FUDR) via a surgically implanted hepatic artery infusion pump (HAIP). Describe the incidence of biliary toxicity and evaluate relevant patterns in the biliary toxicity cohort. METHODS: A single center, retrospective, case-control study included adult colorectal cancer patients with liver metastases who received at least one cycle of FUDR via a surgically implanted HAIP from 1 January 2017, to 1 October 2021. Patients were excluded if they had incomplete records, cholangiocarcinoma diagnosis, or received concurrent mitomycin and FUDR. Biliary toxicity criteria derived from existing HAIP literature were utilized to determine whether patients experienced biliary toxicity. Multiple variables were compared by univariate statistical analysis between the biliary toxicity and non-biliary toxicity cohorts to identify potential risk factors for development of FUDR-induced biliary toxicity. RESULTS: Out of 50 patients who had a HAIP implanted, 39 met the inclusion criteria. Five of the 39 patients (12.7%) included in the analysis met the pre-specified biliary toxicity criteria. No risk factors for biliary toxicity were identified. All five patients who developed biliary toxicity demonstrated elevations in alkaline phosphatase (ALP) prior to meeting the toxicity criteria. CONCLUSION: Biliary toxicity remains a significant and therapy-limiting consequence of FUDR administration. Rising ALP may be an early indicator of subsequent biliary toxicity. Future studies with more patients may identify risk factors that can facilitate risk mitigation strategies.

Predicting Dihydropyrimidine Dehydrogenase Deficiency and Related 5-Fluorouracil Toxicity: Opportunities and Challenges of DPYD Exon Sequencing and the Role of Phenotyping Assays.

Deficiency of dihydropyrimidine dehydrogenase (DPD), encoded by the DPYD gene, is associated with severe toxicity induced by the anti-cancer drug 5-Fluorouracil (5-FU). DPYD genotyping of four recommended polymorphisms is widely used to predict toxicity, yet their prediction power is limited. Increasing availability of next generation sequencing (NGS) will allow us to screen rare variants, predicting a larger fraction of DPD deficiencies. Genotype−phenotype correlations were investigated by performing DPYD exon sequencing in 94 patients assessed for DPD deficiency by the 5-FU degradation rate (5-FUDR) assay. Association of common variants with 5-FUDR was analyzed with the SNPStats software. Functional interpretation of rare variants was performed by in-silico analysis (using the HSF system and PredictSNP) and literature review. A total of 23 rare variants and 8 common variants were detected. Among common variants, a significant association was found between homozygosity for the rs72728438 (c.1974+75A>G) and decreased 5-FUDR. Haplotype analysis did not detect significant associations with 5-FUDR. Overall, in our sample cohort, NGS exon sequencing allowed us to explain 42.5% of the total DPD deficiencies. NGS sharply improves prediction of DPD deficiencies, yet a broader collection of genotype−phenotype association data is needed to enable the clinical use of sequencing data.

Hepatic arterial infusion pump chemotherapy combined with systemic therapy for patients with advanced colorectal liver metastases: Outcomes in a newly established program.

BACKGROUND AND OBJECTIVES: Colorectal liver metastasis (CRLM) is a leading cause of morbidity and mortality in patients with colorectal cancer. Hepatic arterial infusion (HAI) chemotherapy has been demonstrated to improve survival in patients with resected CRLM and to facilitate conversion of technically unresectable disease. METHODS: Between 2016 and 2018, n = 22 HAI pumps were placed for CRLM. All patients received systemic chemotherapy concurrently with HAI floxuridine/dexamethasone. Overall survival (OS) and progression-free survival (PFS) were assessed using the Kaplan-Meier method. RESULTS: HAI pumps were placed in seven patients with completely resected CRLM and 15 patients with unresectable disease. Twenty-one patients received HAI floxuridine with a median of 5 total HAI cycles (interquartile range: 4-7). Biliary sclerosis was the most common HAI-related complication (n = 5, 24%). Of the 13 patients treated to convert unresectable CRLM, 3 (23%) underwent hepatic resection with curative intent after a median of 7 HAI cycles (range: 4-10). For all HAI patients, the mean OS was 26.7 months from CRLM diagnosis, while the median PFS and hepatic PFS from pump placement were 9 and 13 months, respectively. CONCLUSION: Concomitant HAI and systemic therapy can be utilized at multidisciplinary programs for patients with advanced CRLM, both in the adjuvant setting and to facilitate conversion of unresectable disease.

Comparison of Hepatic Arterial Infusion Pump Chemotherapy vs Resection for Patients With Multifocal Intrahepatic Cholangiocarcinoma.

Importance: Intrahepatic cholangiocarcinoma (iCCA) is often multifocal (ie, satellites or intrahepatic metastases) at presentation. Objective: To compare the overall survival (OS) of patients with multifocal iCCA after hepatic arterial infusion pump (HAIP) floxuridine chemotherapy vs resection. Design, Setting, and Participants: In this cohort study, patients with histologically confirmed, multifocal iCCA were eligible. The HAIP group consisted of consecutive patients from a single center who underwent HAIP floxuridine chemotherapy for unresectable multifocal iCCA between January 1, 2001, and December 31, 2018. The resection group consisted of consecutive patients from 12 centers who underwent a curative-intent resection for multifocal iCCA between January 1, 1990, and December 31, 2017. Resectable metastatic disease to regional lymph nodes and previous systemic therapy were permitted. Patients with distant metastatic disease (ie, stage IV), those who underwent resection before starting HAIP floxuridine chemotherapy, and those who received a liver transplant were excluded. Data were analyzed on September 1, 2021. Main Outcomes and Measures: Overall survival in the 2 treatment groups was compared using the Kaplan-Meier method and log-rank test. Results: A total of 319 patients with multifocal iCCA were included: 141 in the HAIP group (median [IQR] age, 62 [53-70] years; 79 [56.0%] women) and 178 in the resection group (median [IQR] age, 60 [50-69] years; 91 [51.1%] men). The HAIP group was characterized by a higher percentage of bilobar disease (88.0% [n = 124] vs 34.3% [n = 61]), larger tumors (median, 8.4 cm vs 7.0 cm), and a higher proportion of patients with 4 or more lesions (66.7% [94] vs 24.2% [43]). Postoperative mortality after 30 days was 0.8% (95% CI, 0.0%-2.1%) in the HAIP group vs 6.2% (95% CI, 2.3%-9.7%) in the resection group (P = .01). The median OS for HAIP was 20.3 months vs 18.9 months for resection (P = .32). Five-year OS in patients with 2 or 3 lesions was 23.7% (95% CI, 12.3%-45.7%) in the HAIP group vs 25.7% (95% CI, 17.9%-37.0%) in the resection group. Five-year OS in patients with 4 or more lesions was 5.0% (95% CI, 1.7%-14.3%) in the HAIP group vs 6.8% (95% CI, 1.8%-25.3%) in the resection group. After adjustment for tumor diameter, number of tumors, and lymph node metastases, the hazard ratio of HAIP vs resection was 0.75 (95% CI, 0.55-1.03; P = .07). Conclusions and Relevance: This cohort study found that patients with multifocal iCCA had similar OS after HAIP floxuridine chemotherapy vs resection. Resection of multifocal intrahepatic cholangiocarcinoma needs to be considered carefully given the complication rate of major liver resection; HAIP floxuridine chemotherapy may be an effective alternative option.

Efficacies of FAEV and EMA/CO regimens as primary treatment for gestational trophoblastic neoplasia.

BACKGROUND: Guidelines recommend etoposide, methotrexate, actinomycin D (EMA)/cyclophosphamide, vincristine (CO) as first-line treatment for high-risk gestational trophoblastic neoplasia (GTN). However, the floxuridine, actinomycin D, etoposide and vincristine (FAEV) regimen is commonly used to treat these patients in China. We conducted a randomised controlled trial to compare the efficacies and toxicities of FAEV and EMA/CO. METHODS: Ninety-four patients with GTN were enrolled between May 2015 and April 2019 and randomly assigned to the FAEV or EMA/CO regimen. The rates of complete remission and relapse and the toxicities were compared in August 2021. RESULTS: Five patients were excluded from the analysis. There were 46 patients in the FAEV group and 43 patients in the EMA/CO group. The complete remission rates following primary treatment were 89.1% and 79.1% (P = 0.193), respectively. The relapse rates were 8.7% and 9.3% (P = 0.604). The apparent incidences of grade 4 myelosuppression were 60.9% and 32.6% (P = 0.008), respectively; however, they became both 32.6% (P = 0.996) after granulocyte colony-stimulating factor support. Other adverse reactions were similar in the two groups. No patient died of disease. CONCLUSION: FAEV has comparable efficacy and toxicity to EMA/CO as the primary treatment for high-risk GTN, and may thus be another first-line choice of chemotherapy. CLINICAL TRIAL REGISTRATION: chictr.org.cn: ChiCTR1800017423.

Hepatic Arterial Infusion Pump Chemotherapy for Unresectable Intrahepatic Cholangiocarcinoma: A Systematic Review and Meta-Analysis.

BACKGROUND: Patients with unresectable intrahepatic cholangiocarcinoma (iCCA) have poor survival. This systematic review describes the survival outcomes of hepatic arterial infusion pump (HAIP) chemotherapy with floxuridine for patients with unresectable iCCA. PATIENTS AND METHODS: A literature search was conducted using the electronic databases PubMed, Medline (Ovid), Embase, Web of Science, Google Scholar, and Cochrane to find studies that reported data on the survival of patients with unresectable iCCA treated with HAIP chemotherapy using floxuridine. The quality of the studies was assessed using the Newcastle-Ottawa quality assessment Scale (NOS). Overall survival (OS) was the primary outcome measure, and progression-free survival (PFS), response rates, resection rates, and toxicity were defined as secondary outcome measures. RESULTS: After removing duplicates, 661 publications were assessed, of which nine studies, representing a total of 478 patients, met the inclusion criteria. Three out of nine studies were phase II clinical trials, one study was a prospective dose-escalation study, and the remaining five studies were retrospective cohort studies. After accounting for overlapping cohorts, 154 unique patients were included for pooled analysis. The weighted median OS of patients with unresectable iCCA treated with HAIP chemotherapy with floxuridine was 29.0 months (range 25.0-39 months). The pooled 1-, 2-, 3-, and 5-year OS were 86.4, 55.5, 39.5, and 9.7%, respectively. CONCLUSION: HAIP chemotherapy with floxuridine for patients with unresectable iCCA was associated with a 3-year OS of 39.5%, which is favorable compared with systemic chemotherapy for which no 3-year survivors were reported in the Advanced Biliary Cancer (ABC) trials.

Adjusting the neuron to astrocyte ratio with cytostatics in hippocampal cell cultures from postnatal rats: A comparison of cytarabino furanoside (AraC) and 5-fluoro-2'-deoxyuridine (FUdR).

Cell culture studies offer the unique possibility to investigate the influence of pharmacological treatments with quantified dosages applied for defined time durations on survival, morphological maturation, protein expression and function as well as the mutual interaction of various cell types. Cultures obtained from postnatal rat brain contain a substantial number of glial cells that further proliferate with time in culture leading to an overgrowth of neurons with glia, especially astrocytes and microglia. A well-established method to decrease glial proliferation in vitro is to apply low concentrations of cytosine arabinoside (AraC). While AraC primarily effects dividing cells, it has been reported repeatedly that it is also neurotoxic, which is the reason why most protocols limit its application to concentrations of up to 5 µM for a duration of 24 h. Here, we investigated 5-fluoro-2'-deoxyuridine (FUdR) as a possible substitute for AraC. We applied concentrations of both cytostatics ranging from 4 µM to 75 µM and compared cell composition and cell viability in cultures prepared from 0-2- and 3-4-day old rat pups. Using FUdR as proliferation inhibitor, higher ratios of neurons to glia cells were obtained with a maximal neuron to astrocyte ratio of up to 10:1, which could not be obtained using AraC in postnatal cultures. Patch-clamp recordings revealed no difference in the amplitudes of voltage-gated Na+ currents in neurons treated with FUdR compared with untreated control cells suggesting replacement of AraC by FUdR as glia proliferation inhibitor if highly neuron-enriched postnatal cultures are desired.

Glutathione catabolism by Enterobacteriaceae species to hydrogen sulphide adversely affects the viability of host systems in the presence of 5'fluorodeoxyuridine.

Reduced glutathione (GSH) plays an essential role in relieving oxidative insult from the generation of free radicals via normal physiological processes. However, GSH can be exploited by bacteria as a signalling molecule for the regulation of virulence. We describe findings arising from a serendipitous observation that when GSH and Escherichia coli were incubated with 5'fluorodeoxyuridine (FUdR)-synchronised populations of Caenorhabditis elegans, the nematodes underwent rapid death. Death was mediated by the production of hydrogen sulphide mainly through the action of tnaA, a tryptophanase-encoding gene in E. coli. Other Enterobacteriaceae species possess similar cysteine desulfhydrases that can catabolise l-cysteine-containing compounds to hydrogen sulphide and mediate nematode killing when worms had been pre-treated with FUdR. When colonic epithelial cell lines were infected, hydrogen sulphide produced by these bacteria in the presence of GSH was also able to inhibit ATP synthesis in these cells particularly when cells had been treated with FUdR. Therefore, bacterial production of hydrogen sulphide could act in concert with a commonly used genotoxic cancer drug to exert host cell impairment. Hydrogen sulphide also increases bacterial adhesion to the intestinal cells. These findings could have implications for patients undergoing chemotherapy using FUdR analogues that could result in intestinal damage.

DNA-Damage-Response-Targeting Mitochondria-Activated Multifunctional Prodrug Strategy for Self-Defensive Tumor Therapy.

We report a novel multifunctional construct, M1, designed explicitly to target the DNA damage response in cancer cells. M1 contains both a floxuridine (FUDR) and protein phosphatase 2A (PP2A) inhibitor combined with a GSH-sensitive linker. Further conjugation of the triphenylphosphonium moiety allows M1 to undergo specific activation in the mitochondria, where mitochondria-mediated apoptosis is observed. Moreover, M1 has enormous effects on genomic DNA ascribed to FUDR's primary function of impeding DNA/RNA synthesis combined with diminishing PP2A-activated DNA repair pathways. Importantly, mechanistic studies highlight the PP2A obtrusion in FUDR/5-fluorouracil (5-FU) therapy and underscore the importance of its inhibition to harbor therapeutic potential. HCT116 cell xenograft-bearing mice that have a low response rate to 5-FU show a prominent effect with M1, emphasizing the importance of DNA damage response targeting strategies using tumor-specific microenvironment-activatable systems.